XIII 



RESPIEATOEY RHYTHM 



451 



conjunctiva, immobility of pupil, inertia and flaccidity of tongue 

 and muscles of jaw, suppression of salivary secretions, marked fall 

 of temperature, inhibition of swallowing reflexes, failure to vomit 

 after injection of apomorphine ; lastly, suspension of any kind of 

 reaction from the cocainised bulbar substance to electrical stimuli, 

 however strong. The possibility that under these conditions there 

 can be paralysis of the spinal, as well as the bulbar centres, owing 

 to spread of the poison, seems to be excluded by the rate at which 

 complete arrest of respiratory movements may occur (less than 

 20 seconds), as well as by phenomena which prove that the 

 excitability of the spinal centres is maintained e.g. rhythmical 

 contraction and relaxation of the sphincter on introduction of the 

 finger into the rectum. 



These results led Aducco to the important conclusion that a 

 true motor centre exists in the bulb, besides the inhibitory centre 



R\ 



MAA^^ 



PIG. 207. Same as preceding, after nine minutes' application of the drug. (Aducco.) Tracing 

 R shows the active and passive inspirations. Followed by complete arrest of respiration. 



to the heart, and that both are paralysed by the local action of 

 cocaine. The paralysis of the cardiac inhibitory centre (formed as 

 we have seen by the nuclei of origin of the accessory) causes 

 acceleration of the beats ; paralysis of the respiratory centre 

 (constituted in all probability by the formatio reticularis) causes 

 arrest of respiratory movements. Hence it is the bulbar respiratory 

 centre that sends co-ordinated rhythmical impulses to the spinal 

 centres of the respiratory muscles. These last centres are, therefore, 

 incapable of any rhythmical activity, independent of that of the 

 bulbar centre. If under certain conditions (as in the experiments 

 of Langendorff, Wertheiiner and others) they show activity 

 independent of the bulb, this activity is not co-ordinated, and is 

 conditioned by the peripheral or central stimuli, of which we have 

 still to study the mechanism. 



The simplest, clearest, and most incontrovertible proof of the 

 absolute dependence of the spinal centres of the respiratory 



